actually that depend on how important trophy is for you, i personally don't mine it EXCEPT the online trophy,

example like the original mass effect, you need a minimum of 3 play through to get platinum, need to play hard mode to unlock

harcore, play harcore to unlock insanity (something like that).

i rarely platinum a game, i only got 1 platinum which is dragon age origin. Even if with or without trophy, i usually play multiple time on sp.